Multi-media clarification systems and methods

ABSTRACT

A media clarifier may have a passageway, an inlet, an outlet above the inlet, a screen, and a media bed with both compressible and incompressible media. The screen may span the passageway. The media bed may be adjacent to the screen when the media clarifier is in an operational state. Particulate matter is removed from a water stream as it passes through the media bed.

RELATED APPLICATIONS

This application claims priority to and is a continuation application ofU.S. application Ser. No. 15/836,628, which was filed on 8 Dec. 2017 andis entitled “MULTI-MEDIA CLARIFICATION SYSTEMS AND METHODS,” which ishereby expressly incorporated by reference in its entirety.

TECHNICAL FIELD

The present invention relates to an apparatus and method for filteringfluids. More specifically, it relates to media clarifiers.

BACKGROUND

Media clarifiers use media to capture particulate matter from a water orwastewater stream. Media, which adsorbs particulate matter, helps removesolids at a faster rate than traditional clarifiers, which do not usemedia. Consequently, media clarifiers can handle larger flows andconsume less space than a traditional clarifier. Accordingly, increasingthe performance of the media employed in a media clarifier is desirable.

SUMMARY

Embodiments of the disclosed subject matter are provided below forillustrative purposes and are in no way limiting of the claimed subjectmatter.

A media clarifier may comprise a vessel defining a passageway for water.The vessel may comprise an inlet for the passageway, an outlet for thepassageway, and a screen intermediate the inlet and the outlet that isdisposed within and spans the passageway. The vessel may place the inletin fluid communication with the screen and the outlet. When the mediaclarifier is in an installed configuration, the outlet may be situatedabove the inlet. The media bed may be disposed within the passagewayintermediate the inlet and the screen. The media bed may comprise bothcompressible media and incompressible media.

Those skilled in the art will further appreciate that in otherembodiments, the present invention is adapted for use with a variety offluid and filtering applications.

BRIEF DESCRIPTION OF THE DRAWINGS

Various embodiments of the invention will become apparent from thefollowing description and appended claims, taken in conjunction with theaccompanying drawings. Understanding that these drawings depict onlyexamples of the invention thereof and are, therefore, not to beconsidered limiting of the invention's scope, particular embodimentswill be described with additional specificity and detail through use ofthe accompanying drawings in which:

FIG. 1 is a side elevation, cross-sectional view of one embodiment of amedia clarifier during normal operation.

FIG. 2 is a side elevation, cross-sectional view of one embodiment of amedia clarifier during a cleaning cycle.

FIG. 3 is an enlarged view of one embodiment of a media bed.

FIG. 4 is a photograph of a mixture of incompressible media interactingwith compressible media.

FIG. 5 is a side elevation, cross-sectional view of one embodiment of amedia clarifier with media in a stratified state.

FIG. 6 is a bar graph showing that fewer cleaning cycles are needed fora filter downstream of a media clarifier when both compressible andincompressible media are used rather than a single type of media in themedia clarifier.

FIG. 7 is a bar graph showing that less water, on average, is wastedwhen both compressible and incompressible media are used rather than asingle type of media.

FIG. 8 is a line chart showing increased efficiency when bothcompressible and incompressible media are used rather than a single typeof media based on two sample runs.

FIG. 9 is a flow diagram illustrating one embodiment of a method forutilizing a media clarifier.

FIG. 10 is a flow diagram illustrating one embodiment of a method forcleaning a media clarifier.

In accordance with common practice, the various features illustrated inthe drawings may not be drawn to scale. Accordingly, the dimensions ofthe various features may be arbitrarily expanded or reduced for clarity.In addition, some of the drawings may be simplified for clarity. Thus,the drawings may not depict all of the components of a given apparatus(e.g., device) or method. Finally, like reference numerals may be usedto denote like features throughout the specification and figures.

DETAILED DESCRIPTION

Various aspects of the disclosure are described below. It should beapparent that the teachings herein may be embodied in a wide variety offorms and that any specific structure, function, or both being disclosedherein is merely representative. Based on the teachings herein, oneskilled in the art should appreciate that an aspect disclosed herein maybe implemented independently of any other aspects and that two or moreof these aspects may be combined in various ways, even if thatcombination is not shown or disclosed in the same figure or portion ofthe disclosure. Further, the disclosed apparatuses and methods may bepracticed using structures or functionality in addition to disclosedsubject matter based on information known to one of skill in the art.

The term “an embodiment,” “an alternative embodiment” or “oneembodiment” may refer to various configurations or embodiments of thedisclosed apparatuses, systems, or methods in the singular or pluralform, rather than referring to a single, particular embodiment.

In the figures, certain components may appear many times within aparticular drawing. However, only certain instances of the component maybe identified in the figures to avoid an unnecessary repetition ofreference numbers and lead lines. According to the context provided inthe description while referring to the figures, reference may be made toa specific one of that particular component or multiple instances, evenif the specifically referenced instance or instances of the componentare not identified by a reference number and lead line in the figure(s).

Media clarifiers may also be referred to as media clarification systems,filter systems, media filters, upward filters, or any combination ofthese terms. Media clarifiers may, in various embodiments, rely in wholeor in part on principles of adsorption. Particulate matter can befiltered from a water stream as it passes through a treatment columncontaining adsorbent media. Media may be comprised of many members, suchas beads, sand, or synthetic fibers; the word “media” refers to both asingular and plural number of these members. The system may be used invarious water applications, such as drinking water or wastewatertreatment. The water stream provided to the system may be pressurized,using, for example, a pump or gravity. Particulate matter may includedirt, sand, minerals, biological material, and/or other types ofmaterial, and may also include flocculated particles comprisingchemicals such as flocculants and/or coagulants.

One type of media used in a media filter is incompressible.Incompressible media does not flex or deform under pressures typicallyencountered in water filtration systems (e.g., pressures generated in 5to 150 inches of water). In various embodiments of the invention,incompressible media comprises small beads, which may be as small as 1millimeter. The beads may be made of high-density polyethylene (HDPE) orother natural or synthetic materials. Other examples of incompressiblemedia include other plastics, such as Acrylonitrile Butadiene Styrene(ABS), low-density polyethylene (LDPE), or natural materials, such ascharcoal or wood. Incompressible media may adsorb particulate matter onthe media surface and within interstitial space between adjacent mediabeads. The surface of incompressible media may comprise a disturbedsurface, such as by scarification, sanding, or other rougheningapplications, which makes the incompressible media more adsorbent.

Media may also be compressible. One example of compressible mediautilizes bundles of elongated plastic fibers. The bundles of elongatedplastic fibers may be tightly bound with a clip, ring, staple, crimp, orclamp at the center and fan out at the ends. These bundles, when bound,may be spherical in shape. In various embodiments, the fibers may bemade from a combination of polypropylene and polyethylene terephthalateand may be approximately three (3) inches in length. In suchembodiments, when the fibers are crimped or clamped together, eachfibrous ball may have a diameter of approximately 1.5 to 2 inches. Invarious embodiments of the invention, compressible media may flex orchange size or shape under pressure. Thus, the compressible media may bemore flexible than the incompressible media measured, for example, usingthe flexural modulus, which indicates a tendency to bend rather thanbreak. Compressible media may capture particulate matter by anycombination of adsorption on its surface or in its fibers, capturewithin the interstitial spaces between media, or capture by thecompression and/or flexion of the media's shape.

The media bed may be comprised, in various embodiments, of sufficientmedia to span the cross-sectional area of the water column along ahorizontal dimension

The media bed may also be thick enough to allow the water to flow overenough media surface area to capture a sufficient quantity ofparticulate matter to make the filter useful, which in variousembodiments, may be at least six (6) inches in depth. If more than onetype of media is used in the media bed, each type of media may besufficient in number to span the cross-sectional area of the watercolumn along a horizontal dimension of a certain depth (e.g., at leastthree (3) inches deep) without the other type of media. Alternatively, acombination of the types of media may be of a certain depth.

Media, whether compressible or incompressible, in various embodiments,may have a specific gravity of less than 1. However, various factorssuch as the specific gravity of the fluid, the quantity and mass ofsolids in the fluid, and the speed of the fluid may allow use of mediathat has a specific gravity of 1 or greater to rise to the filter bed.

Compressible media can typically hold more particulate matter thanincompressible media but generally cannot capture finer particles whileit is uncompressed. For this reason, some compressible media filtersemploy a system to compress the media. However, while the media iscompressed, it cannot adsorb as much particulate matter as it can in anuncompressed state. The disclosed subject matter combines the two typesof media, resulting in an unexpected synergistic effect. Compressiblemedia may be used to capture larger particles, while incompressiblemedia captures smaller particles. The combination of the two types ofmedia causes the system to capture more particles. It also removes ahigher percentage of particulate matter than either type of media can byitself. Additionally, it allows the filter to operate without acompression system.

In various embodiments, the size of the compressible media may be muchlarger than the incompressible media (e.g., five (5) to twenty (20)times larger). In various alternative embodiments, compressible andincompressible media may be more similar in size (i.e., compressiblemedia may be less than five (5) times larger). Referring to FIG. 1, oneembodiment of a media clarifier 101 is illustrated. In the illustratedembodiment, the media clarifier 101 may comprise a vessel 102 defining apassageway 104 for water 117 with an inlet 106, and an outlet 108. Theoutlet 108 may also be referred to as the effluent outlet 108. The mediaclarifier 101 may further comprise a screen 110 intermediate the inlet106 and the outlet 108. The screen 110 may span the passageway 104. Theoutlet 108 may be a collection trough, pipe, or other mechanism forreceiving effluent water 117. The vessel 102 may place the inlet 106 influid communication with the screen 110 and the outlet 108. In theinstalled configuration, as illustrated in FIG. 1, the outlet 108 may besituated above the inlet 106.

In the installed configuration, the media clarifier 101 may include avertical dimension 115 a, a horizontal dimension 115 b, and a transversedimension 115 c, as illustrated on the dimensional guide 115. In thisapplication, the term “above” indicates at a higher elevation along avertical dimension 115 a. In contrast, the term “directly above”signifies that a first element is located at a higher elevation along avertical dimension 115 a relative to a second element with the firstelement and the second element at least overlapping along a horizontaldimension 115 b. As a result, in various embodiments, the outlet 108 mayor may not be directly above the inlet 106, but the outlet 108 maysimply be above (i.e., at a higher elevation along a vertical dimension115 a). Influent water 117 enters the media clarifier 101 through aninlet 106, which may be controlled by a fluid control mechanism 113(e.g., a pump or valve). The water 117 may then pass through adistribution header 103 (sometimes referred to as a water distributionheader 103) and enter into the passageway 104, which may, in variousembodiments, also be referred to or comprise a treatment column. Water117 flows upward through the media bed 105, which may comprise bothcompressible media 109 and incompressible media 107. In variousembodiments, the media bed 105 may comprise and/or be referred to as afilter bed 105. Solids, such as particulate matter, in the influentstream of water 117 may be separated from the stream of water 117 byadsorption on to the media surfaces, by capture using the filamentousfibers or other compressible bodies, and by capture within theinterstitial spaces between the media 107, 109. The media bed 105 may beretained within the system by the screen 110, which may be described asa hold-down screen system 110 or a retention screen 110. Clarified water117 passes through the retention screen 110 and exits via the outlet 108(which may be located above the hold-down screen system 110) and thenflows out of the media clarifier 101.

One or more of the types of media in the media bed 105 may, in certainembodiments, be buoyant. In various alternative embodiments, one or moreof the types of media in the media bed 105 may be non-buoyant (such thatnon-buoyant media resides at the bottom of the vessel 102 when the mediaclarifier 101 is not in use), but may be propelled upward in response tothe flow of water 117 through the vessel 102.

In various embodiments of the invention, as solids are captured, adifferential pressure develops across the media bed 105. As thedifferential pressure increases, the compressible media 109 iscompressed, which in turn tightens the interstitial spaces to retain theparticulate matter. As the developing differential pressure nears themaximum allowable pressure (e.g., a predetermined differentialpressure), the media clarifier 101 may be transitioned to a cleaningcycle to remove the captured particulate matter. In various embodiments,the differential pressure is regulated by constricting or expanding thevolume of the media bed 105. This can be done with a mechanical wall, aflexible housing controlled by hydrostatic pressure, or other mechanismsthat can alter the volume of the media bed 105 (not illustrated in FIG.1). In certain embodiments, the predetermined differential pressure maybe ascertained using a first and second pressure sensor 131 a-b. Thefirst pressure sensor 131 a may be disposed within the passageway 104downstream of or within the media bed 105, while a second pressuresensor 131 b may be disposed within the passageway 104 upstream of orwithin the media bed 105, as illustrated in FIG. 1. In variousalternative embodiments, only the pressure sensor 131 b upstreamrelative to the media bed 105 is used in the media clarifier 101 basedon the assumption that the pressure downstream of the media bed 105 willremain constant or at least relatively constant.

In various embodiments of the invention, a bottom screen positionedintermediate the inlet and the retention screen (not illustrated inFIG. 1) serves as a lower boundary for the media bed.

Referring to FIG. 2, one embodiment of the present invention isillustrated in a cleaning cycle. In the installed configuration (asshown in FIG. 2), the media clarifier 101 may include a verticaldimension 115 a, a horizontal dimension 115 b, and a transversedimension 115 c, as illustrated on the dimensional guide 115. In theillustrated embodiment, the media clarifier 101 may be transitioned to acleaning cycle using, in part, a flow direction control mechanism 121(e.g., an actuating cylinder 121), which may, in various embodiments,raise a waste gate to allow the waste stream to exit the treatmentvessel 102 through a wastewater opening 112 (an opening other than theoutlet 108). In various embodiments, a lower edge or lip of thewastewater opening 112 is lower (along a vertical dimension 115 a) thanthe lower edge or lip of the outlet 108. Accordingly, activating a fluiddirection control mechanism 121 may simply allow water 117 passingthrough the media bed 105 to exit through the wastewater opening 112before it reaches the lower lip or edge of the outlet 108. Those skilledin the art will appreciate that various types of flow direction controlmechanisms 121 may be employed. In various alternative embodiments, forexample, the flow direction control mechanism 121 may comprise a pair ofindependently controlled gates or valves.

In addition, in the cleaning cycle, a gas 123 (e.g., air) may beintroduced by operating a gas control mechanism 130 (e.g., by opening avalve or activating a pump). The introduced gas 123 may flow through adistribution header 132 (sometimes referred to as a gas distributionheader 132). In various embodiments, the gas control mechanism 130 anddistribution header 132 may be referred to collectively as a gas or airinjection mechanism assembly. In various embodiments, the bulk densityof the combined gas 123 and water 117 is less than the bulk density ofthe compressible media 109 and/or the incompressible media 107 (becauseof the introduction of the gas 123) causing all or a portion of themedia bed 105 to sink (not illustrated in FIG. 2). This action expandsthe media bed 105 to allow release of the captured particulate matter.The introduced gas 123 also causes collisions between the media 107, 109to dislodge particulate matter that has adhered to the media surface. Invarious embodiments, the introduction of the gas 123 into the water 117,which causes the media bed to sink and assist with the release ofcaptured particulate matter, may be referred to as fluidization. Thewater 117 may thus pass through the fluid control mechanism 113 anddistribution header 103 and travel in an upward direction through themedia bed 105 to carry the released particulate matter away from themedia clarifier 101. After a period of time, if the gas controlmechanism 130 comprises a valve, the gas control mechanism 130 may beclosed, or, if the gas control mechanism 130 comprises a pump, the pumpmay be deactivated. Water 117 may continue to pass through the vessel102 to remove the remaining particulate matter and to assist inrestoring the media bed 105 to earlier levels. The actuating cylinder121 may be activated to close the waste gate 120 to terminate thecleaning cycle.

FIG. 3 comprises an enlarged view of one embodiment of a media bed 105.In the illustrated embodiment, incompressible media 107 is mixed withcompressible media 109 to create additional interstitial gaps with whichto capture solids 341 (which comprise one type of particulate matter).In various embodiments, a portion of the incompressible media 107 has ascarified surface to aid with adsorption. The incompressible media 107that has a scarified surface may be referred to as scarifiedincompressible media 107 a.

FIG. 4 is a closeup photograph of compressible media 109 andincompressible media 107 disposed in water 117.

FIG. 5 illustrates one embodiment of media 107, 109 in a stratifiedstate within a media clarifier 101. In the installed configuration (asshown in FIG. 5), the media clarifier 101 may include a verticaldimension 115 a, a horizontal dimension 115 b, and a transversedimension 115 c, as illustrated on the dimensional guide 115. During acleaning cycle and prior to returning the media clarifier 101 tooperational state, as illustrated in FIG. 5, a layer of incompressiblemedia 107 may remain on top of a layer of compressible media 109. Itshould be noted that the media clarifier 101 may have: an operationalstate, in which water 117 flows through the vessel and the clarifier isoperated to remove particulate matter from the influent stream of water117; a non-operational state, in which no or little water 117 flowsthrough the media clarifier 101; and a cleaning state, in which themedia clarifier is operated to dislodge particulate matter from themedia 107, 109 and flush the dislodged particulate matter from the mediaclarifier 101.

In various embodiments, a layer of compressible media 109 may remainabove a layer of incompressible media 107 (i.e., the media bed 105 is ina stratified state). This can be done by manipulating the media withstreams of gas 123 and/or water 117. As illustrated in FIG. 5, theincompressible media 107 and compressible media 109 (which, in certainembodiments, may also be referred to as fibrous balls 109) may bestratified into discrete regions. For example, before a finalflush-to-waste step (which comprises a part of the cleaning cycle), theincompressible media 107 and compressible media 109 may be stratified byadjusting the gas 123 and water 117 to segregate and stack one type ofmedia on top of the other. One example of such an adjustment isincreasing the water rate and altering the gas flow rate according tothe sequence identified in Table 1, which is provided below:

TABLE 1 Stratification Gas (e.g., Air) Water Time Steps scfm/ft² gpm/ft²seconds 1 0 0 60 2 <1 5 60 3 0 12.5 60 4 3 12.5 60

One skilled in the art will understand that the foregoing constitutesonly one embodiment of a method for achieving media in a stratifiedstate. Other approaches including varying the gas flow rate, the waterflow rate, or the amount of time may be utilized to stratify the media.

FIG. 6 is a bar graph illustrating the average number of cleaning cyclesper day for a filter (a “downstream filter”) situated downstream of amedia clarifier. The decreased number of cleaning cycles for thedownstream filter indicates that a media clarifier with incompressibleand compressible media 107, 109 provides improved removal of particulatematter. Because the media clarifier is capturing more particulatematter, additional cleaning cycles are or may be required for the mediaclarifier. The vertical axis of FIG. 6 identifies the average number ofcleaning cycles per day for the downstream filter, while the horizontalaxis identifies the quantity of particulate matter within the stream ofwater 117 received by the media clarifier, measured in NTU(Nephelometric Turbidity Units). A higher NTU value indicates a higherquantity of particulate matter within the incoming stream. FIG. 6 showsthat a downstream filter following a media clarifier with both types ofmedia will have fewer cleaning cycles per day compared to a downstreamfilter following a media clarifier with only one type of media.

FIG. 7 is a bar graph illustrating net average percent water production.The vertical axis of FIG. 7 identifies the net average percent of waterproduced, which may be defined in accordance with Equation 1.

$\begin{matrix}{\left\lbrack {{Net}\mspace{14mu} {Average}\mspace{14mu} {Percent}\mspace{14mu} {Water}\mspace{14mu} {Production}} \right\rbrack = {\frac{\left\lbrack {{Average}\mspace{14mu} {Total}\mspace{14mu} {Water}\mspace{14mu} {Produced}} \right\rbrack}{\begin{matrix}{\left\lbrack {{Average}\mspace{14mu} {Total}\mspace{14mu} {Water}\mspace{14mu} {Produced}} \right\rbrack +} \\\left\lbrack {{Average}\mspace{14mu} {Total}\mspace{14mu} {Water}\mspace{14mu} {Wasted}} \right\rbrack\end{matrix}} \times 100}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

A higher number indicates that less water 117 is wasted. The horizontalaxis identifies the quantity of particulate matter within the incomingstream of water 117, measured in NTU. FIG. 7 shows that a mediaclarifier with both types of media wastes less water 117 than a mediaclarifier with only one type of media.

FIG. 8 is a line graph illustrating the percentage of particulate matterremoved by two sample runs. The vertical axis of FIG. 8 identifies thepercentage of particulate matter removed, measured in NTU, while thehorizontal axis represents runtime in minutes. The line graph of FIG. 8indicates that a media clarifier with both types of media removes ahigher percentage of NTU than a media clarifier using onlyincompressible media.

FIG. 9 is a flowchart illustrating one embodiment of a method 901 forutilizing a media clarifier. Step 910 involves operating a fluid controlmechanism 113 to cause water 117 to flow through the passageway 104 fromthe inlet 106 to the outlet 108 in an operational state. As utilizedherein, the water 117 may include particulate matter at least during aportion of the time in which the water 117 is moving through thepassageway 104. The fluid control mechanism 113 may comprise one or moreof various types of valves or pumps. Accordingly, in variousembodiments, a valve may control the flow of water 117 into thepassageway 104 with the water 117 being propelled, for example, by theforce of gravity or by a pump. Thus, in various embodiments, opening avalve may cause water 117 to flow through the passageway 104, whileclosing the valve may terminate the flow of water 117 through thepassageway 104. If a pump is utilized as a fluid control mechanism 113,activating the pump will cause water 117 to flow through the passageway104, while deactivating the pump will result in water 117 not flowingthrough the passageway 104.

In step 920, in a non-operational state, the fluid control mechanism 113is operated to cause water 117 not to flow through the passageway 104from the inlet 106 to the outlet 108. In various embodiments, step 920may involve closing a valve and/or deactivating a pump.

In step 930, in a cleaning state, the fluid control mechanism 113 may beoperated to cause water 117 to flow through the passageway 104 from theinlet 106 to a wastewater opening 112 and/or operating a gas controlmechanism 130 to cause gas 123 to be injected into the passageway 104.The cleaning state of step 930 may encompass a series of stages, asdiscussed in connection with Table 1, or a single stage. Step 930 mayalso comprise inducing the media bed 105 to transition into a fluidizedstate and/or stratified state, as discussed above. Additional detailregarding the cleaning state will be provided in connection with FIG.10. It should be noted that steps 910, 920, 930 may be performed in anyorder, not necessarily in the order illustrated in FIG. 9.

FIG. 10 is a flowchart illustrating one embodiment of a method 1001 forcleaning a media clarifier. In step 1010, a gas control mechanism 130 isoperated to inject gas 123 into a passageway 104 and/or a fluid controlmechanism 113 is operated to inject water 117 into the passageway 104 toagitate the media bed 105 to dislodge solids captured by the media bed105. As noted above, this step 1010 may involve a single or a pluralityof stages (see, e.g., Table 1) and may involve transitioning the mediabed 105 into a fluidized and/or a stratified state.

In step 1020, a fluid direction control mechanism 121 may be operated toredirect a flow of water 117 passing through the media bed 105, suchthat dislodged solids exit the passageway 104 through one or moreopenings (e.g., a wastewater opening 112) other than the outlet 108. Asnoted above, various types of fluid direction control mechanisms 121 maybe employed, such as an actuating arm coupled to a waste gate, and/or aplurality of valves or gates. As noted above, in various embodiments,the lower edge or lip of the wastewater opening 112 may be lower than alower edge or lip of the outlet 108. Accordingly, in such embodiments,merely allowing the water 117 to access the wastewater opening causeswater to flow through the wastewater opening 112 before reaching theoutlet 108.

It is understood that any specific order or hierarchy of steps in anydisclosed process is an example of an approach. Based upon designpreferences, it is understood that the specific order or hierarchy ofsteps in the processes may be rearranged while remaining within thescope of the present disclosure. The accompanying method claims presentelements of the various steps in a sample order, and are not meant to belimited to the specific order or hierarchy presented.

The previous description of the disclosed aspects is provided to enableany person skilled in the art to make or use the present disclosure.Various modifications to these aspects will be readily apparent to thoseskilled in the art, and the generic principles defined herein may beapplied to other aspects without departing from the scope of thedisclosure. Thus, the present disclosure is not intended to be limitedto the aspects shown herein but is to be accorded the widest scopeconsistent with the principles and novel features disclosed.

What is claimed is: 1-10. (canceled)
 11. A method of operating a mediaclarifier during a cleaning cycle, said media clarifier comprising: avessel defining an interior; a retention screen disposed within andspanning said interior, wherein said retention screen divides saidinterior into a first portion and a second portion, wherein at least aportion of said second portion is above said first portion along avertical dimension of said media clarifier; an inlet for introducingwater into said first portion of said interior; a water distributionheader disposed in said first portion of said interior for receivingsaid water from said inlet; an outlet for conveying said water out ofsaid vessel, wherein said retention screen is disposed downstream ofsaid inlet and upstream of said outlet; a gas distribution headerdisposed in said first portion of said interior for introduction of gasinto said first portion; a media bed disposed within said interior anddownstream of said inlet, said media bed comprising both compressiblemedia and incompressible media; a fluid control mechanism forcontrolling introduction of said water via said water distributionheader into said first portion; a gas control mechanism for controllingsaid introduction of said gas via said gas distribution header into saidfirst portion; and a fluid direction control mechanism for directingsaid water, downstream of said retention screen, either through saidoutlet or through a wastewater opening, wherein said method comprises:during a step of said cleaning cycle, operating said fluid controlmechanism to introduce none of said water into said first portion, andoperating said gas control mechanism to introduce none of said gas intosaid first portion; during an ensuing step of said cleaning cycle,operating said fluid control mechanism to introduce said water at afirst water flow rate into said first portion, and operating said gascontrol mechanism to introduce said gas at a first gas flow rate intosaid first portion, said ensuing step being subsequent in time withrespect to said step; during a following step of said cleaning cycle,operating said fluid control mechanism to introduce said water at asecond water flow rate into said first portion, said second water flowrate being greater than said first water flow rate, and operating saidgas control mechanism to introduce none of said gas into said firstportion, said following step being subsequent in time with respect tosaid ensuing step; during a subsequent step of said cleaning cycle,operating said gas control mechanism to introduce said gas at a secondgas flow rate into said first portion, said second gas flow rate beinggreater than said first gas flow rate, such that during at least aportion of said cleaning cycle, said incompressible media and saidcompressible media are stratified into discrete regions in that a layerof said incompressible media is disposed above a layer of saidcompressible media along said vertical dimension, said subsequent stepbeing subsequent in time with respect to said following step.
 12. Themethod of claim 11, wherein said compressible media is more flexiblethan said incompressible media.
 13. The method of claim 12, wherein asize ratio of individual compressible media units in a dry state of saidcompressible media to individual incompressible media units in a drystate of said incompressible media is greater than 4 to
 1. 14. Themethod of claim 13, wherein a specific gravity of said incompressiblemedia is less than 1, and a specific gravity of said compressible mediais 1 or greater.
 15. The method of claim 14, wherein said specificgravity of said compressible media and said specific gravity of saidincompressible media are different by at least 0.02.
 16. The method ofclaim 15, wherein said specific gravities of said incompressible mediaand said compressible media are less than one.
 17. The method of claim16, wherein at least a portion of said incompressible media has at leastone roughened surface.
 18. The method of claim 17, wherein said gascontrol mechanism comprises a valve.
 19. The method of claim 18, whereinduring at least a portion of said cleaning cycle, a bulk density of acombination of said water and said gas injected into said water is lessthan a bulk density of at least a portion of said media bed.
 20. Themethod of claim 19, wherein said media bed is at least six inches indepth along said vertical dimension when said media clarifier is in anoperational state.
 21. The method of claim 11, wherein said first gasflow rate is less than 1 standard cubic foot per minute per square footof surface area (scfm/ft²).
 22. The method of claim 21, wherein saidfirst water flow rate is 5 gallons per minute per square foot of surfacearea (gpm/ft²).
 23. The method of claim 22, wherein said second waterflow rate is 12.5 gallons per minute per square foot of surface area(gpm/ft²).
 24. A method of operating a media clarifier during a cleaningcycle, said media clarifier comprising: a vessel defining an interior; aretention screen disposed within and spanning said interior, whereinsaid retention screen divides said interior into a first portion and asecond portion, wherein at least a portion of said second portion isabove said first portion along a vertical dimension of said mediaclarifier; an inlet for introducing water into said first portion ofsaid interior; a water distribution header disposed in said firstportion of said interior for receiving said water from said inlet; anoutlet for conveying said water out of said vessel, wherein saidretention screen is disposed downstream of said inlet and upstream ofsaid outlet; a gas distribution header disposed in said first portion ofsaid interior for introduction of gas into said first portion; a mediabed disposed within said interior and downstream of said inlet, saidmedia bed comprising both compressible media and incompressible media; afluid control mechanism for controlling introduction of said water viasaid water distribution header into said first portion; a gas controlmechanism for controlling said introduction of said gas via said gasdistribution header into said first portion; and a fluid directioncontrol mechanism for directing said water, downstream of said retentionscreen, either through said outlet or through a wastewater opening,wherein said method comprises: during a step of said cleaning cycle,operating said fluid control mechanism to introduce said water at afirst water flow rate into said first portion, and operating said gascontrol mechanism to introduce said gas at a first gas flow rate intosaid first portion; during a subsequent step of said cleaning cycle,operating said fluid control mechanism to introduce said water at asecond water flow rate into said first portion, said second water flowrate being greater than said first water flow rate, and operating saidgas control mechanism to introduce none of said gas into said firstportion such that during at least a portion of said cleaning cycle, saidincompressible media and said compressible media are stratified intodiscrete regions in that a layer of said incompressible media isdisposed above a layer of said compressible media along said verticaldimension, said subsequent step being subsequent in time with respect tosaid step.
 25. The method of claim 24, further comprising: during aproceeding step of said cleaning cycle, operating said fluid controlmechanism to introduce none of said water into said first portion, andoperating said gas control mechanism to introduce none of said gas intosaid first portion, said proceeding step being prior in time withrespect to said step.
 26. The method of claim 25, wherein said first gasflow rate is less than 1 standard cubic foot per minute per square footof surface area (scfm/ft²).
 27. The method of claim 26, wherein saidfirst water flow rate is 5 gallons per minute per square foot of surfacearea (gpm/ft²), and wherein said second water flow rate is 12.5 gallonsper minute per square foot of surface area (gpm/ft²).
 28. The method ofclaim 27, wherein a specific gravity of said compressible media and aspecific gravity of said incompressible media are different by at least0.02.
 29. A method of operating a media clarifier during a cleaningcycle, said media clarifier comprising: a vessel defining an interior; aretention screen disposed within and spanning said interior, whereinsaid retention screen divides said interior into a first portion and asecond portion, wherein at least a portion of said second portion isabove said first portion along a vertical dimension of said mediaclarifier; an inlet for introducing water into said first portion ofsaid interior; a water distribution header disposed in said firstportion of said interior for receiving said water from said inlet; anoutlet for conveying said water out of said vessel, wherein saidretention screen is disposed downstream of said inlet and upstream ofsaid outlet; a gas distribution header disposed in said first portion ofsaid interior for introduction of gas into said first portion; a mediabed disposed within said interior and downstream of said inlet, saidmedia bed comprising both compressible media and incompressible media; afluid control mechanism for controlling introduction of said water viasaid water distribution header into said first portion; and a gascontrol mechanism for controlling said introduction of said gas via saidgas distribution header into said first portion, wherein said methodcomprises: during a step of said cleaning cycle, operating said fluidcontrol mechanism to introduce said water at a first water flow rateinto said first portion, and operating said gas control mechanism tointroduce said gas at a first gas flow rate into said first portion;during a subsequent step of said cleaning cycle, operating said fluidcontrol mechanism to introduce said water at a second water flow rateinto said first portion, said second water flow rate being greater thansaid first water flow rate, and operating said gas control mechanism tointroduce none of said gas into said first portion such that during atleast a portion of said cleaning cycle, said incompressible media andsaid compressible media are stratified into discrete regions along saidvertical dimension, said subsequent step being subsequent in time withrespect to said step.
 30. The method of claim 29, further comprising:during a proceeding step of said cleaning cycle, operating said fluidcontrol mechanism to introduce none of said water into said firstportion, and operating said gas control mechanism to introduce none ofsaid gas into said first portion, said proceeding step being prior intime with respect to said step.